Coated tool and cutting tool

ABSTRACT

A coated tool may include a base member including a first surface, and a coating layer located at least on the first surface of the base member. The coating layer may include a first layer located on the first surface and including a titanium compound, and a second layer contactedly located on the first layer and including aluminum oxide. The second layer may include an orientation coefficient Tc(0012) of 3.0 or more by X-ray diffraction analysis. The coating layer may include a plurality of voids located in a direction along an interface between the first layer and the second layer, and an average value of widths of the voids in a direction along the interface is smaller than an average value of distances between the voids adjacent to each other in a cross section orthogonal to the first surface.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a national stage entry according to 35 U.S.C. § 371 of PCT Application No. PCT/JP2019/034597 filed on Sep. 3, 2019, which claims priority to Japanese Application No. 2018-166095 filed on Sep. 5, 2018, which are entirely incorporated herein by reference.

TECHNICAL FIELD

The present disclosure relates to a coated tool for use in a cutting process.

BACKGROUND

As a coated tool for use in a cutting process, such as a turning process and a milling process, a coated tool is discussed in, for example, Patent Document 1 (Japanese Unexamined Patent Publication No. 2015-182209). The coated tool discussed in Patent Document 1 may include a configuration in which a coating layer is located on a surface of a base member composed of cemented carbide or the like. The coating layer may include a layer (titanium compound layer) including a compound of titanium (Ti), and a layer (aluminum oxide layer) including aluminum oxide (Al₂O₃). In the coated tool described in Patent Document 1, a plurality of voids may be formed at an interface between the titanium compound layer and the aluminum oxide layer. Impact relaxation effect may be obtainable because of the plurality of voids.

Patent Document 2 (Japanese Patent Publication No. 6026468) discusses that the coated tool suitable for cutting steels may be obtained by controlling a texture coefficient Tc(hkl) of an aluminum oxide layer and I₂₂₀/I₃₁₁ of a TiCN layer in a combination of a MTCVD TiCN layer and an aluminum oxide layer.

SUMMARY

A coated tool of the present disclosure may include a base member including a first surface, and a coating layer located at least on the first surface of the base member. The coating layer may include a first layer located on the first surface and including a titanium compound, and a second layer contactedly located on the first layer and including aluminum oxide. The second layer may include an orientation coefficient Tc(0012) of 3.0 or more by X-ray diffraction analysis. The coating layer may include a plurality of voids located in a direction along an interface between the first layer and the second layer, and an average value of widths of the voids in a direction along the interface may be smaller than an average value of distances between the voids adjacent to each other in a cross section orthogonal to the first surface.

A cutting tool of the present disclosure may include a holder including a bar shape which extends from a first end to a second end and including a pocket located at a side of the first end, and the above-mentioned coated tool which is located at the pocket.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view illustrating a coated tool of the present disclosure.

FIG. 2 is a sectional view taken along line A-A in the coated tool illustrated in FIG. 1.

FIG. 3 is an enlarged view in the vicinity of a coating layer in the coated tool illustrated in FIG. 2.

FIG. 4 is an enlarged view illustrating a non-limiting embodiment of the region B1 illustrated in FIG. 3.

FIG. 5 is an enlarged view illustrating another non-limiting embodiment of the region B1 illustrated in FIG. 3.

FIG. 6 is a plan view illustrating a cutting tool of the present disclosure.

FIG. 7 is an enlarged view in a region B2 illustrated in FIG. 6.

DETAILED DESCRIPTION

A coated tool of the present disclosure is described in detail below with reference to the drawings. For the sake of description, each of the drawings referred to in the following illustrates, in a simplified form, only main members necessary for the explanation. Hence, the coated tool is capable of including any structural member not illustrated in the drawings referred to. Dimensions of the members in each of the drawings are not ones which faithfully represent dimensions of actual structural members and dimension ratios of these members.

<Coated Tool>

A coated tool 1 of the present disclosure includes a base member 3 and a coating layer 5 as illustrated in FIGS. 1 and 2. The base member 3 includes a first surface 7 (an upper surface in FIG. 2), a second surface 9 adjacent to the first surface 7 (a side surface in FIG. 2), and a cutting edge 11 located at least on a part of a ridge line where the first surface 7 intersects with the second surface 9.

The base member 3 has a quadrangular plate shape in the example shown in FIG. 1, and the first surface 7 has a quadrangular shape. The number of the second surfaces 9 is therefore four. At least a part of the first surface 7 is a rake surface region, and at least a part of the second surface 9 is a flank surface region. The shape of the base member 3 is not limited to the quadrangular plate shape, and for example, the first surface 7 may have a triangular, pentagonal, hexagon or circular shape. Alternatively, the base member 3 may have a columnar shape besides the plate shape.

The coating layer 5 is located at least on the first surface 7 of the base member 3. The coating layer 5 may be located only on the first surface 7 or on a surface other than the first surface 7 in the base member 3. The coating layer 5 is also located on the second surface 9 in addition to the first surface 7. The coating layer 5 is included for the purpose of improving characteristics of the coated tool 1 during a cutting process, such as wear resistance and chipping resistance.

The coating layer 5 includes a first layer 13 and a second layer 15 as illustrated in FIG. 3. The first layer 13 is located on the first surface 7 and includes a titanium compound. The second layer 15 is contactedly located on the first layer 13 and includes aluminum oxide (Al₂O₃).

Examples of the titanium compound included in the first layer 13 include titanium carbide, nitride, oxide, carbonitride, carbon oxide and oxycarbonitride. The first layer 13 may be configured to include only one of the above compounds or, alternatively, may be configured to include a plurality of kinds of the above compounds.

The first layer 13 may be made into a single layer or, alternatively, may include a configuration in which a plurality of layers are laminated one on another as long as it includes a titanium compound. For example, the first layer 13 may include a configuration in which a titanium nitride layer 17 and a titanium carbonitride layer 19 are laminated one on another. Bondability between the base member 3 and the first layer 13 becomes higher if the first layer 13 includes the titanium nitride layer 17 as a layer contacting the base member 3. The titanium nitride layer 17 and the titanium carbonitride layer 19 include titanium nitride and titanium carbonitride as a main component, respectively, and may include other components. The term “main component” denotes a component having the largest value in mass % among values of other components.

The coating layer 5 may be composed only of the first layer 13 and the second layer 15 or, alternatively, may include a layer other than these layers. For example, a different layer may be interposed between the base member 3 and the first layer 13 or, alternatively, a different layer may be located on the second layer 15.

The titanium carbonitride layer 19 may include a configuration in which a plurality of regions different in composition are laminated one on another. For example, the titanium carbonitride layer 19 may include a configuration in which a so-called MT (moderate temperature) first region 19 a, and a so-called HT (high temperature) second region 19 b are laminated one on another.

In cases where the first layer 13 includes the first region 19 a and the second region 19 b, the first layer 13 may further include an intermediate region 19 c between the first region 19 a and the second region 19 b.

A boundary between the layers and a boundary between the regions can be determined, for example, by observing an electron microscope photograph (a scanning electron microscope (SEM: Scanning Electron Microscope) photograph or a transmission electron microscope (TEM: Transmission Electron Microscope) photograph). Identification can be performed by the ratio of elements constituting each layer and differences in a size or an orientation of a crystal.

The aluminum oxide included in the second layer 15 is α-alumina (α-Al₂O₃). By using α-alumina in the second layer 15, heat resistance of the coated tool 1 can be enhanced. The second layer 15 may be configured to include only one of the above compounds or, alternatively, may include a plurality of kinds of the above compounds.

The crystal of the aluminum oxide included in the second layer 15 can be evaluated, for example, by carrying out X-ray diffraction (XRD: X-Ray Diffraction) analysis using CuKα radiation and θ to 2θ scan and by observing a distribution of peak values.

The first layer 13 may include a component other than the titanium compound, and the second layer 15 may include a component other than the aluminum oxide. For example, bondability between the first layer 13 and the second layer 15 is improved if the first layer 13 includes the aluminum oxide and the second layer 15 includes the titanium compound.

The coating layer 5 includes voids 21 in an interior of the first layer 13 as illustrated in FIG. 4. Specifically, the coating layer 5 includes the plurality of voids 21 located side by side in the first layer 13 in a direction along a boundary 16 between the first layer 13 and the second layer 15 in a cross section orthogonal to the first surface 7 of the base member 3.

In the coated tool of the present disclosure, since an average value of widths w1 of the voids 21 in a direction parallel to the first surface 7 is smaller than a distance between the voids 21 adjacent to each other, namely, an average value of widths w2 at the first portion X in the cross section orthogonal to the first surface 7, high impact resistance in the voids 21 is obtainable while reducing degradation of strength of the first portion X. It is therefore possible to obtain the impact relaxation effect because of the voids 21 while reducing degradation of the bondability between the first layer 13 and the second layer 15.

In the coated tool 1 of the present disclosure, a texture coefficient Tc(0012) of the aluminum oxide, which is the second layer 15, exceeds 3. As a result, the second layer 15 has high wear resistance. Tc(0012) is measured by carrying out CuKα ray scan and X-ray scan of θ to 2θ from an upper surface of the second layer 15.

The coated tool 1 of the present disclosure has high impact resistance and high wear resistance by including the above-mentioned first layer 13 and the above-mentioned second layer 15.

The orientation coefficient Tc(hkl) can be calculated by the following formula.

Tc(hkl)={I(hkl)/I ₀(hkl)}/[(⅛)×Σ{I(HKL)/I ₀(HKL)}]

Here, (HKL) is crystal planes of (012), (104), (110), (113), (116), (300), (214) and (0012). I(HKL) and I(hkl) are peak intensities of the peaks attributed to each crystal plane detected in the X-ray diffraction analysis of the titanium compound of the first layer. I₀(HKL) and I₀(hkl) are standard diffraction intensities of each crystal plane described in JCPDS card No. 00-010-0173.

In evaluating the average value of the widths w1 of the voids 21 in the direction parallel to the first surface 7, it is unnecessary to evaluate the widths w1 of all the voids 21 existing in the cross section orthogonal to the first surface 7, but the average value may be evaluated by an average value of the widths w1 of approximately 5 to 10 voids 21 located side by side in the cross section. For example, a 10 μm square region including the boundary 16 between the first layer 13 and the second layer 15 may be extracted in the cross section orthogonal to the first surface 7, and the widths w1 of the voids 21 in the region may be measured. An average value of the widths w2 of the first portion X may be evaluated by an average value of distances between approximately 5 to 10 voids 21 located side by side in the cross section. There may be other cases of determining an average value in the present disclosure. An average value of approximately 5 to 10 values may be obtained in each of the cases.

The voids 21 may exist in the first layer 13. Besides the configuration in which the voids 21 are located in the first layer 13 as illustrated in FIG. 4, it is possible to employ, for example, a configuration in which the voids 21 are located in each of the first layer 13 and the second layer 15 as illustrated in FIG. 5. An imaginary line segment along the boundary 16 between the first layer 13 and the second layer 15 is indicated by a chain line in FIG. 5, and the voids 21 located in the second layer 15 may be located along the boundary 16 between the first layer 13 and the second layer 15.

The phrase that “the voids 21 are located along the boundary 16 between the first layer 13 and the second layer 15” denotes that distances from the plurality of voids 21 to the boundary 16 between the first layer 13 and the second layer 15 fall within a range of ±20% of an average value thereof.

In cases where the first layer 13 includes titanium carbonitride as a titanium compound and the second layer 15 includes α-alumina as aluminum oxide from the viewpoint of heat resistance and durability of the coated tool 1, the durability of the coated tool 1 can be further enhanced if the plurality of voids 21 are located in the first layer 13.

The reason for this is as follows. Hardness of the titanium carbonitride is higher but impact resistance thereof is lower than that of α-alumina. Therefore, if the voids 21 are located in the first layer 13, impact resistance because of the voids 21 can be enhanced in the first layer 13, and the durability of the coated tool 1 can be further enhanced.

Although no particular limitations are imposed on size of the voids 21, the size is settable to, for example, 20-200 nm. The impact relaxation effect because of the voids 21 can be enhanced if the size of the voids 21 is 20 nm or more. It is easy to maintain the strength of the first layer 13 if the size of the voids 21 is 200 nm or less. The term “size of the voids 21” denotes a maximum value of the widths w1 of the voids 21 in the cross section orthogonal to the first surface 7.

No particular limitations are imposed on shape of the voids 21. The impact resistance can be further enhanced while reducing a ratio of the voids 21 if the width w1 in the direction parallel to the first surface 7 is larger than a height h1 in the direction orthogonal to the first surface 7, in other words, if the average value of the widths w1 of the voids 21 in the direction parallel to the first surface 7 is larger than an average value of the heights h1 of the voids 21 in the direction orthogonal to the first surface 7 in the cross section orthogonal to the first surface 7. The reason for this is as follows.

During a cutting process of a workpiece for the purpose of manufacturing a cut product, the coating layer 5 is susceptible to a cutting load in the direction orthogonal to the first surface 7. If the voids 21 have such a shape that the width w1 in the direction parallel to the first surface 7 is larger than the height h1 in the direction orthogonal to the first surface 7, the cutting load can be absorbed in a wide range of the voids 21 without making the voids 21 larger than necessary. This makes it possible to further enhance the impact resistance while reducing the ratio of the voids 21. The term “heights h1 of the voids 21 in the direction orthogonal to the first surface 7” denotes a maximum value of the heights h1 of the voids 21 in the direction orthogonal to the first surface 7.

Specifically, the cutting load tends to be absorbed in a wide range of the voids 21 if a ratio of the average value of the widths w1 of the voids 21 in the direction orthogonal to the first surface 7 to the average value of the heights h1 of the voids 21 in the direction parallel to the first surface 7 is 1.2 or more. Additionally, if the above ratio is 2 or less, it is easy to ensure a deformation amount of the voids 21 in the direction orthogonal to the first surface 7, thus leading to stable absorption of the cutting load in the voids 21.

If the average value of the heights h1 of the voids 21 in the direction orthogonal to the first surface 7 is smaller than Rz where Rz is a maximum height of the boundary between the first surface 7 and the second surface 9 in the cross section orthogonal to the first surface 7, it is easy to reduce degradation of the durability of the coating layer 5.

The coated tool 1 of the present disclosure has the enhanced impact resistance because of deformation of the first portion X located between the voids 21 adjacent to each other and because of deformation of the plurality of voids 21 in the first layer 13. If an average value of widths of the voids 21 in the direction orthogonal to the first surface 7 is smaller than Rz, an imaginary line connecting the voids 21 adjacent to each other is indicated by a zigzag shape that is bent larger than the width of the void 21.

In cases where the imaginary line is indicated by the above shape, even if a crack occurs at one of the first portions X, the crack is less likely to propagate to the first portion X located adjacent to the first portion X with the crack. The durability of the coating layer 5 is therefore less likely to degrade.

The durability of the coating layer 5 is also less likely to degrade if an average value of distances d1 from the voids 21 to the boundary 16 between the first layer 13 and the second layer 15 is larger than an average value of widths w2 of the first portions X in the cross section orthogonal to the first surface 7. The term “distance d1 from the voids 21 to the boundary 16 between the first layer 13 and the second layer 15” denotes a minimum value of the distance to the boundary 16 in the voids 21.

The reason for this is as follows. Because, in comparison with the first portions X, the above case ensures a sufficient distance from the voids 21 to the boundary 16 between the first layer 13 and the second layer 15, even if a crack occurs at one of the first portions X, the crack is less likely to reach the boundary 16 between the first layer 13 and the second layer 15. The bondability between the first layer 13 and the second layer 15 is less likely to degrade because the crack is less likely to reach the boundary 16 between the first layer 13 and the second layer 15.

The voids 21 are located in the first layer 13 and located away from the boundary between the first layer 13 and the second layer 15. The bondability between the first layer 13 and the second layer 15 is less likely to degrade while achieving enhanced impact resistance in the coating layer 5 if an average value of the distances d1 from the voids 21 to the boundary 16 between the first layer 13 and the second layer 15 is larger than an average value of the heights h1 of the voids 21 in the direction orthogonal to the first surface 7 in the cross section orthogonal to the first surface 7.

The reason for this is as follows. Because, in comparison with the size of the voids 21, the distance from the voids 21 to the boundary 16 between the first layer 13 and the second layer 15 can be sufficiently ensured, even if the voids 21 are deformed due to absorption of the cutting load, the boundary 16 between the first layer 13 and the second layer 15 is not deformed, or the deformation amount becomes sufficiently small. The bondability between the first layer 13 and the second layer 15 is less likely to degrade because the boundary 16 between the first layer 13 and the second layer 15 is less subjected to large deformation.

Examples of material of the base member 3 include inorganic materials, such as cemented carbide, cermet and ceramics. The material of the base member 3 is not limited to these materials.

Examples of composition of cemented carbide include WC(tungsten carbide)-Co, WC—TiC(titanium carbide)-Co and WC—TiC—TaC(tantalum carbide)-Co. Specifically, WC, TiC and TaC are hard particles, and Co is a binding phase. The cermet is a sintered composite material obtainable by compositing metal into a ceramic component. Specific examples of the cermet include compounds composed mainly of TiC, TiCN or TiN (titanium nitride).

The base member 3 includes a through hole 23 that passes through the first surface 7 and a surface located on an opposite side of the first surface 7. The through hole 23 is usable for inserting a fixing member that is intended to fix the coated tool 1 to a holder. Examples of the fixing member include a screw and a clamping member.

The size of the base member 3 is not particularly limited. For example, a length of one side of the first surface 7 is settable to approximately 3-20 mm. A height from the first surface 7 to the surface located on the opposite side of the first surface 7 is settable to approximately 5-20 mm.

<Manufacturing Method>

A non-limiting embodiment of a method for manufacturing the coated tool of the present disclosure is described below.

Firstly, a mixed powder is manufactured by suitably adding metal powder, carbon powder or the like to inorganic powder selected from carbide, nitride, carbonitride and oxide or the like, which are capable of forming a hard alloy constituting a base member 3 by sintering, and then by mixing them together. Subsequently, a molded body is manufactured by molding the mixed powder into a predetermined tool shape with the use of a known molding method. Examples of the molding method include press molding, casting molding, extrusion molding and cold isostatic pressing. The base member 3 is manufactured by sintering the molded body in vacuum or a non-oxidizing atmosphere. A surface of the base member 3 may be then subjected to polishing process and honing process as needed.

Subsequently, a coating layer 5 is deposited on the surface of the base member 3 by chemical vapor deposition (CVD) method.

The first step is to deposit a titanium nitride layer 17 (underlayer) in the first layer 13. A first mixed gas used as a reaction gas is manufactured by mixing 0.5-10 vol % of titanium tetrachloride gas and 10-60 vol % of nitrogen gas into hydrogen (H₂) gas. The titanium nitride layer 17 is deposited in a temperature range of 830-870° C. by introducing the first mixed gas at a gas partial pressure of 10-20 kPa into a chamber.

The next step is to deposit a first region 19 a in the first layer 13. A second mixed gas is manufactured by blending 0.5-10 vol % of titanium tetrachloride gas, 5-60 vol % of nitrogen gas and 0.1-3 vol % of acetonitrile gas into hydrogen gas. The MT-first region 19 a is deposited in a temperature range of 830-870° C. by introducing the second mixed gas at a gas partial pressure of 6-12 kPa into the chamber.

The next step is to deposit an intermediate layer 19 c. A third mixed gas is manufactured by blending 3-30 vol % of titanium tetrachloride gas, 3-15 vol % of methane gas, 5-10 vol % of nitrogen gas and 0.5-10 vol % of carbon dioxide (CO₂) gas into hydrogen gas. The intermediate region 19 c having a thickness of approximately 50-300 nm is deposited in a temperature range of 980-1050° C. by introducing the third mixed gas at a gas partial pressure of 6-12 kPa into the chamber. Voids 21 are formable in the intermediate region 19 c because the third mixed gas includes carbon dioxide gas. With the above conditions, a coated tool 1 in which an average value of widths w1 of the voids 21 in a direction parallel to the first surface 7 is smaller than an average value of distances w2 between the voids 21 adjacent to each other in a cross section orthogonal to the first surface 7 can be manufactured.

Additionally, since the thickness of the intermediate region 19 c is as small as approximately 50-300 nm, it becomes possible to align the voids 21 formed in the intermediate region 19 c in a direction along the boundary 16 between the first layer 13 and the second layer 15.

The next step is to deposit a second region 19 b in the first layer 13. A fourth mixed gas is manufactured by blending 1-4 vol % of titanium tetrachloride gas, 5-20 vol % of nitrogen gas, 0.1-10 vol % of methane gas and 0.5-10 vol % of carbon dioxide gas into hydrogen gas. The HT-second region 19 b having a thickness of approximately 0.3-3 μm is deposited in a temperature range of 950-1050° C. by introducing the fourth mixed gas at a gas partial pressure of 5-45 kPa into the chamber.

The next step is to deposit a second layer 15. In a deposition temperature of 950-1050° C., at a gas pressure of 5.5 kPa and with the following reaction gas composition, a fifth mixed gas is manufactured by blending 1.0-1.4 vol % of aluminum trichloride (AlCl₃) gas, 4.5-5.0 vol % of carbon dioxide (CO₂) gas and 1.7-1.9 vol % of hydrogen chloride (HCl) gas into hydrogen gas, and an aluminum oxide layer having a thickness of approximately 0.1 μm is formed. Furthermore, in the same deposition temperature, at the same gas pressure and with the following reaction gas composition, a sixth mixed gas is manufactured by blending 1.1-1.3 vol % of aluminum trichloride (AlCl₃) gas, 4.5-5.0 vol % of carbon dioxide (CO₂) gas, 2.0-3.4 vol % of hydrogen chloride (HCl) gas and 0.5 to 0.7 vol % of hydrogen sulfide (H₂S) into hydrogen gas, and an aluminum oxide layer having a thickness of approximately 5 μm is formed. In this way, the second layer 15 is formed. If the second layer 15 is formed under the above-mentioned condition, the orientation coefficient Tc(0012) becomes 3.0 or more.

Thereafter, as needed, a polishing process is carried out on a part of the surface of the deposited coating layer 5 at which the cutting edge 11 is located. If the polishing process is carried out, a workpiece is less likely to be welded onto the cutting edge 11, thus leading to the coated tool 1 having more excellent fracture resistance.

The above manufacturing method is a non-limiting embodiment of the method for manufacturing the coated tool 1. Hence, the coated tools 1 are not limited to ones which are manufactured by the above manufacturing method. For example, a third layer including TiN may be deposited separately on the second layer 15.

In order to manufacture the coated tool 1 in which an average value of the widths w1 of the voids 21 in the direction parallel to the first surface 7 is smaller than an average value of the distances w2 of the voids 21 adjacent to each other in the cross section orthogonal to the first surface 7, the carbon dioxide gas may be adjusted to 0.5-5 vol % during the deposition of the intermediate region 19 c.

In order to manufacture the coated tool 1 in which the average value of the widths w1 of the voids 21 in the direction parallel to the first surface 7 is larger than an average value of the heights h1 of the voids 21 in the direction orthogonal to the first surface 7 in the cross section orthogonal to the first surface 7, time adjustment may be carried out during the deposition of the intermediate region 19 c so that the intermediate region 19 c is deposited in a thickness of approximately 50-150 nm.

In order to manufacture the coated tool 1 in which an average value of the distances d1 from the voids 21 to the boundary 16 is larger than an average value of the heights h1 of the voids 21 in the direction orthogonal to the first surface 7 in the cross section orthogonal to the first surface 7, time adjustment may be carried out during the deposition of the intermediate region 19 c so as to be deposited in a thickness of approximately 50-150 nm, and thereafter the second region 19 b in the first layer 13 may be deposited in a thickness of approximately 0.5-3 μm.

In order to manufacture the coated tool 1 in which an average value of the distances d1 from the voids 21 to the boundary 16 is larger than an average value of the distances w2 of the voids 21 adjacent to each other in the cross section orthogonal to the first surface, the second region 19 b in the first layer 13 may be deposited so as to be thicker than the average value of the distances w2 of the voids 21 adjacent to each other.

<Cutting Tool>

A cutting tool 101 of the present disclosure is described below with reference to the drawings.

As illustrated in FIGS. 6 and 7, the cutting tool 101 of the present disclosure includes a holder 105 having a bar-shaped body that extends from a first end (an upper side in FIG. 6) to a second end (a lower side in FIG. 6) with a pocket 103 located at a side of the first end, and the above-mentioned coated tool 1 located at the pocket 103. In the cutting tool 101 of the present disclosure, the coated tool 1 is attached so that a part of the ridge line which is usable as a cutting edge is protruded from a front end of the holder 105.

The pocket 103 is a part that permits attachment of the coated tool 1. The pocket 103 includes a seating surface parallel to a lower surface of the holder 105, and a constraining side surface inclined relative to the seating surface. The pocket 103 opens into a side of the first end of the holder 105.

The coated tool 1 is located at the pocket 103. A lower surface of the coated tool 1 may be in a direct contact with the pocket 103. Alternatively, a sheet may be held between the coated tool 1 and the pocket 103.

The coated tool 1 is attached so that the part of the ridge line which is usable as the cutting edge is protruded outward from the holder 105. The coated tool 1 is attached to the holder 105 by a screw 107. Specifically, the coated tool 1 is attached to the holder 105 in such a manner that screw parts are engaged with each other by inserting the screw 107 into the through hole 23 of the coated tool 1, and by inserting a front end of the screw 107 into a screw hole (not illustrated) formed in the pocket 103.

For example, steel and cast iron are usable as the holder 105. High toughness steel may be used in a non-limiting embodiment.

The examples shown in FIGS. 6 and 7 have illustrated and described the cutting tools for use in the so-called turning process. Examples of the turning process include inner diameter processing, outer diameter processing and grooving process. The cutting tools are not limited to ones which are used for the turning process. For example, the coated tools 1 of the above non-limiting embodiments are applicable to the cutting tools for use in the milling process.

DESCRIPTION OF THE REFERENCE NUMERALS

-   -   1 coated tool     -   3 base member     -   5 coating layer     -   7 first surface     -   9 second surface     -   11 cutting edge     -   13 first layer     -   15 second layer     -   16 boundary (boundary between first layer and second layer)     -   17 titanium nitride layer     -   19 titanium carbonitride layer     -   19 a first region     -   19 b second region     -   19 c intermediate region     -   21 void     -   23 through hole     -   101 cutting tool     -   103 pocket     -   105 holder     -   107 fixing screw 

1. A coated tool, comprising: a base member comprising a first surface; and a coating layer located at least on the first surface of the base member, wherein the coating layer comprises: a first layer located on the first surface and comprising a titanium compound, and a second layer located on and in contact with the first layer and comprising aluminum oxide; the second layer comprises an orientation coefficient Tc(0012) of 3.0 or more by X-ray diffraction analysis; and the coating layer further comprises a plurality of voids located in a direction along a boundary between the first layer and the second layer, and an average value of widths of the voids in the direction along the boundary is less than an average value of distances between respective voids of the plurality of voids adjacent to each other in a cross section orthogonal to the first surface.
 2. The coated tool according to claim 1, wherein the first layer further comprises titanium carbonitride, and the second layer further comprises α-alumina.
 3. The coated tool according to claim 1, wherein an average value of widths of the respective voids in a direction parallel to the first surface is greater than an average value of heights of the respective voids in a direction orthogonal to the first surface in the cross section orthogonal to the first surface.
 4. The coated tool according to claim 1, wherein an average value of distances from the respective voids to the boundary is greater than an average value of heights of the respective voids in a direction orthogonal to the first surface in the cross section orthogonal to the first surface.
 5. The coated tool according to claim 1, wherein an average value of distances from the respective voids to the boundary is greater than an average value of distances between the respective voids adjacent to each other in a direction parallel to the first surface in the cross section orthogonal to the first surface.
 6. A cutting tool, comprising: a holder comprising a bar shape which extends from a first end to a second end and comprises a pocket located at a side of the first end; and the coated tool according to claim 1, which is located at the pocket. 